While differences do exist between familial and sporadic ankylosing spondylitis, key similarities suggest that the two conditions can be treated the same way, according to a new study presented at the annual meeting of the Canadian Rheumatology Association.
“AS [ankylosing spondylitis] patients with a family history of AS are not very different from patients without any family history,” Nigil Haroon, MD, of the University Health Network in Toronto, explained in an interview. “They have similar disease activity as measured by markers of inflammation [and] similar disease severity as assessed by radiographic scoring for spinal damage.”
Dr. Haroon, along with his coinvestigators – including Bruce Sheng, MD,of the same institution, who presented the study at the meeting – prospectively followed AS patients satisfying the New York criteria for a period of 15 years, collecting data on 888 eligible subjects who were eventually included in the study. Of the subjects included, 74% were male, the average age was 45.6 years (standard deviation, 13.7 years), and average disease duration was 15 years (SD, 11.5 years).
Dr. Nigil Haroon
The investigators found some similarities between the 177 (20%) patients with familial AS who had at least one first- or second-generation relative with the disease and the 711 with sporadic AS. Anti–tumor necrosis factor (anti-TNF) treatment failed in 23.1% of familial AS patients and 23.6% of sporadic disease patients based on the lack of a “sustained clinical effect” for more than 1 year. There were also no differences found between the groups in clinical and radiographic severity of disease.
However, patients with familial AS did record earlier onset of disease (22.5 years vs. 24.3 years; P = .016), longer disease duration (17.4 years vs. 14.3 years; P = .003), and higher HLA-B27 positivity (90% vs. 65%; P less than .001), along with higher rates of uveitis, psoriatic arthritis, and inflammatory bowel disease.
“Some of the findings are expected, including the higher prevalence of HLA-B27 due to gene sharing in the family. ... The higher B27 sharing may also affect the uveitis prevalence as well in familial AS,” Dr. Haroon explained. “The similar radiographic progression rates and treatment responses are interesting findings.”
In terms of the ramifications of these findings, Dr. Haroon stated that clinicians should reevaluate how they prescribe drugs to their AS patients.
“The high likelihood of uveitis in familial AS patients – 43% versus 29% – may affect the choice of treatment as all drugs are not equally effective in uveitis,” he said. “As the family history of extra-articular manifestations is high in familial AS, it remains to be seen if a lower threshold for investigating symptoms suggestive of IBD/uveitis will decrease delays in diagnosis of these conditions in individuals with a family history of AS.”
Moving forward from here, Dr. Haroon called for family studies, especially those including families with multiple individuals affected with AS, as these can help identify genetic risk factors that may be contribute to the development of AS.
“There is paucity of data on familial AS,” Dr. Haroon said. “The strength of this study is the large dataset.”
The study was funded by the Canadian Rheumatology Association’s Summer Research Program, which supported Dr. Sheng. Dr. Sheng and Dr. Haroon did not report any other relevant financial disclosures.